Previously spring clips for locking the plug of a fluid duct into a socket comprised either a pair of parallel transverse holes for the ends of a hairpin-type clip or a split annulus fitting into radially aligned grooves in the plug and socket. The split ends of the annulus were intergrally connected to orthogonal parallel legs to be pinched together for reducing the circumference of the annulus into the groove in the plug to unlock the plug from the socket. Such a split ring annulus only bridged the two radially aligned grooves most effectively adjacent the legs, in that the sides of the annulus diametrically opposite the single split had substantially no radial movement whatsoever that could insure bridging between the cooperating radial grooves in the plug and socket. Furthermore, the integral connection between the legs and the resilient loop that may connect them and/or the split locking annulus, had this resilient movement in the radial width of the loop and annulus, which produces a much stiffer and harder to pinch clip than if the resiliency were in the thickness of loop strip.